Two related human research projects are proposed as part of this program project (PPG) that require quantitative assessment of sleep and wakefulness. Polysomnography (PSG) is the gold standard for such assessments. We have therefore developed a plan for the continuation of a PSG Core as part of this Program, in support of these projects, to ensure the accurate and efficient acquisition, analysis and interpretation of PSG derived measures of sleep and wakefulness. Over the years, PSG methodology has undergone dramatic changes that allow for the collection and analysis of large digitized data sets. Moreover, these developments have resulted in a high degree of sophistication of PSG hardware and software that require a team of specialists who operate and maintain these tools. The general objective of the proposed PSG Core is to provide a knowledge base and an integrated infrastructure to maintain high quality standards in PSG in support of Projects 1 and 2 as well as the Biostatistical and Analytic Core within the program. Specifically, the objectives of the PSG Core will include the following activities: 1. Acquisition and maintenance of PSG equipment and supplies 2. Training of technical research staff at the BWH Center for Clinical Investigation (CCI) in equipment use and instrumentation of research subjects for PSG 3. Assisting in PSG quality assurance at the CCI, and providing technical advice to staff and investigators 4. Archival of digitized PSG data 5. Vigilance state scoring of PSG recordings, and scoring of slow eye movements as a measure of attention failures in wake recordings 6. Quantitative analysis of the sleep EEG with Fast Fourier Transform-routine based spectral analysis in order to obtain measures of homeostatic sleep pressure and circadian sleep drive